Tribological properties of composite Ti(N,O,C) coatings containing hard amorphous carbon layers

Ti–Ti(N,O,C)–(Ti-C)n composite coatings with a thickness of about 1 μm were deposited on stainless steel substrates by continuous and pulsed arc discharge methods. The coatings were found to have a coefficient of friction in the range of 0.1–0.2, critical load for the coating delamination under a scratch test of 5.7–7.3 N, and microhardness of 21⊁25 GPa. Despite the comparatively small difference in values of the microhardness of the tested coatings, their service life under a pin-on-disk test varied by a factor of about 40. The mechanical properties of the upper layers were found to strongly affect the composite coatingʹs service life and be dependent on the design and the deposition strategy of a top (Ti-C)n multilayer film containing a diamond-like carbon layer.